Equilibrium Cross Section of River Channels With Cohesive Erodible Banks

Predicting the equilibrium cross section of natural rivers has been widely investigated in fluvial morphology. Several approaches have been developed to meet this aim, starting from regime equations to the empirical formulations of Parker et al. (2007) and Wilkerson and Parker (2011), who proposed quasi-universal relations for describing bankfull conditions in sand and gravel bed rivers. Nevertheless, a general physics-based framework is still missing, and it remains an open issue to better clarify the basic mechanisms whereby a river selects its width. In this contribution we focus our attention on lowland rivers with cohesive banks, whose resistance to erosion is crucial to control the river width. In particular, we formulate a theoretical model that evaluates the equilibrium width of river cross sections modeling the interaction between the core flow in the central part of the section and the boundary layer that forms in the vicinity of the cohesive banks. The model computes the cross-section equilibrium configuration by which the shear stresses on the banks equal a critical threshold value. These stresses are computed by partitioning the total shear stress into an effective grain roughness component and a form component (Kean and Smith, 2006a). The model is applied to a large data set, concerning both sand and gravel bed rivers, and it is used to determine the relations expressing the channel width and the bankfull flow depth to the bankfull discharge, which appear to provide a unitary description of bankfull hydraulic geometry

How should eosinophilic cystitis be treated in patients with chronic granulomatous disease?

Chronic granulomatous disease (CGD) is a primary immunodeficiency resulting from the absence or malfunction of oxidative mechanism in phagocytic cells. The disease is due to a mutation in one of four genes that encode subunits of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. Affected patients experience severe infections and granuloma formation due to exuberant inflammatory responses. Some evidence suggests that eosinophilic cystitis (EC) is included in the spectrum of inflammatory manifestations. EC is an inflammatory disease, rare in childhood, which may require different, nonstandardized therapeutic approaches, ranging from antihistamines to cyclosporine

Crystal-mush reactivation by magma recharge: Evidence from the Campanian Ignimbrite activity, Campi Flegrei volcanic field, Italy

International audienceProcesses of crystal-mush remobilization by mafic magma recharges are often related to the outpouring of largevolumes of silicic melt during caldera-forming eruptions. This occurred for the Campanian Ignimbrite (CI) erup-tion (Campi Flegrei, Italy), which produced a voluminous trachy-phonolitic ignimbrite in southern-central Italyabout 40 ka ago. We focussed on the proximal-CI deposits at San Martino that are composed of a main sequenceof early-erupted, crystal-poor units and a late-erupted (post-caldera collapse) crystal-rich Upper Pumice FlowUnit (UPFU). Detailed micro-analytical geochemical data were performed on glasses and crystals of pyroclastsfrom these deposits and coupled with Sr-Nd isotopic measurements on glasses. Results show that the CI eruptionwas fed by two distinct melts for the early-erupted units and the late UPFU, respectively. The glasses of the early-erupted units have negative Eu anomalies and show more evolved compositions and higher Nd isotope ratiosthan those of the UPFU, which have positive Eu/Eu*. The magmas of the early units formed the main volume oferuptible meltof the CI reservoir, and are interpretedashaving beenextractedfrom cumulate crystal-mushwith-out a vertical geochemical gradient within the magma reservoir. The data indicate that the generation of thedistinctive UPFU melts involved the injection of a new batch of mafic magma into the base of the CI reservoir.The mafic magma allowed heating and reactivation of the CI crystal-mush by melting of low-Or sanidines(+/−low-An plagioclases), leaving high-An plagioclases and high-Mg# clinopyroxenes as residual phases anda crystal-mush melt, made of 20% of the initial mush interstitial melt (with a composition similar to the early-erupted units) and 80% of sanidine melt. When the mush crystallinity was sufficiently reduced, the maficmagma was able to penetrate into the reactivated crystal-mush, mixing with variable proportions of crystal-mush melt and generating cooler hybrid melts, which underwent further crystallization of high-Or sanidine atvariable degrees (10–25%). Finally, possibly a short time before the eruption, the UPFU magmas were able tomix and mingle with the crystal-poor eruptible melts still persisting in the CI reservoir at the time of UPFU emis-sion. We suggest that the complex mechanisms described for the magma evolution feeding the CI eruption mayoccur whenever a crystal-mush is reactivated by new mafic magma input

Data on unveiling the occurrence of transient, multi-contaminated mafic magmas inside a rhyolitic reservoir feeding an explosive eruption (Nisyros, Greece)

This data article includes the description and the geochemical and mineralogical dataset of 67 pyroclastic rock samples from the Upper Pumice (UP) explosive activity of Nisyros volcano (eastern South Aegean Active Volcanic Arc). A detailed field and petrographic description of the studied outcrops and samples are reported, including representative photomicrographs and SEM images, whole-rock major and trace elements compositions of 31 representative samples and Sr-Nd isotope ratios on 22 selected samples. Analytical methods and conditions used for data acquisition are also reported. The UP eruption produced a stratigraphic sequence constituted by a basal fallout deposit, gradually substituted by pyroclastic density current (PDC) deposits; these are overlaid by a lag-breccia unit, and the sequence is closed by a grey ash flow level. The juvenile is mainly constituted by white-yellow, moderately crystalline pumice with rhyolitic composition and homogenous Sr-Nd isotope values. Variable amounts of dense, grey, crystalline juvenile lapilli clasts (CRC, Crystal-Rich Clast), with rounded shape and less evolved composition (andesite to dacite) are also present in the deposit. These mafic CRCs are peculiar due to their large variability in textures (from distinctive diktytaxitic to strongly fragmented structure without a defined fabric) and in the geochemical and isotopic composition. The data acquired were fundamental to reconstruct the complex and peculiar history of ascent, storage and differentiation/assimilation processes of these mafic melts before their intrusion into the shallow, rhyolitic magma chamber, with important implication on the possible eruption trigger during the more recent explosive phase of activity at Nisyros volcano. Moreover, the geochemical and isotopic analyses provide new original data to the general knowledge of the Aegean volcanics. All the data reported in this paper are related to the research article Braschi et al. (2022

High-precision in situ 87Sr/86Sr analyses through micro-sampling on solid samples: applications to Earth and Life Sciences

An analytical protocol for high-precision, in situ microscale isotopic investigations is presented here, which combines the use of a high-performing mechanical microsampling device and high-precision TIMS measurements on micro-Sr samples, allowing for excellent results both in accuracy and precision. The present paper is a detailed methodological description of the whole analytical procedure from sampling to elemental purification and Sr-isotope measurements. The method offers the potential to attain isotope data at the microscale on a wide range of solid materials with the use of minimally invasive sampling. In addition, we present three significant case studies for geological and life sciences, as examples of the various applications of microscale 87Sr/86Sr isotope ratios, concerning (i) the pre-eruptive mechanisms triggering recent eruptions at Nisyros volcano (Greece), (ii) the dynamics involved with the initial magma ascent during Eyjafjallajökull volcano’s (Iceland) 2010 eruption, which are usually related to the precursory signals of the eruption, and (iii) the environmental context of a MIS 3 cave bear, Ursus spelaeus. The studied cases show the robustness of the methods, which can be also be applied in other areas, such as cultural heritage, archaeology, petrology, and forensic sciences